Radiative Decay of Υ into a Scalar Glueball

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We study the radiative decay of Υ into a scalar glueball Υ→ γGₛ using QCD factorization. We find that for this process the non-perturbative effects can be factorized into a matrix element well defined in non-relativistic QCD (NRQCD) and the gluon distribution amplitude. The same NRQCD matrix element appears also in leptonic decay of Υ and therefore can be determined from data. In the asymptotic limit the gluon distribution amplitude is known up to a normalization constant. Using a QCD sum-rule calculation for the normalization constant, we obtain Br(Υ→ γGₛ) to be in the range (1 2)× 10⁻³. We also discuss some of the implications for Υ→ γfᵢ decays. Near future data from CLEO-III can provide crucial information about scalar glueball properties.